CN114335480B - Core-shell carbon-coated doped lithium iron phosphate, and preparation method and application thereof - Google Patents
Core-shell carbon-coated doped lithium iron phosphate, and preparation method and application thereof Download PDFInfo
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- iron phosphate
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- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 title claims abstract description 111
- 239000011258 core-shell material Substances 0.000 title claims abstract description 57
- 238000002360 preparation method Methods 0.000 title claims abstract description 14
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 58
- 150000001875 compounds Chemical class 0.000 claims abstract description 48
- 238000000034 method Methods 0.000 claims abstract description 48
- TUSDEZXZIZRFGC-UHFFFAOYSA-N 1-O-galloyl-3,6-(R)-HHDP-beta-D-glucose Natural products OC1C(O2)COC(=O)C3=CC(O)=C(O)C(O)=C3C3=C(O)C(O)=C(O)C=C3C(=O)OC1C(O)C2OC(=O)C1=CC(O)=C(O)C(O)=C1 TUSDEZXZIZRFGC-UHFFFAOYSA-N 0.000 claims abstract description 47
- 239000001263 FEMA 3042 Substances 0.000 claims abstract description 47
- LRBQNJMCXXYXIU-PPKXGCFTSA-N Penta-digallate-beta-D-glucose Natural products OC1=C(O)C(O)=CC(C(=O)OC=2C(=C(O)C=C(C=2)C(=O)OC[C@@H]2[C@H]([C@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)[C@@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)[C@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)O2)OC(=O)C=2C=C(OC(=O)C=3C=C(O)C(O)=C(O)C=3)C(O)=C(O)C=2)O)=C1 LRBQNJMCXXYXIU-PPKXGCFTSA-N 0.000 claims abstract description 47
- LRBQNJMCXXYXIU-NRMVVENXSA-N tannic acid Chemical compound OC1=C(O)C(O)=CC(C(=O)OC=2C(=C(O)C=C(C=2)C(=O)OC[C@@H]2[C@H]([C@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)[C@@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)[C@@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)O2)OC(=O)C=2C=C(OC(=O)C=3C=C(O)C(O)=C(O)C=3)C(O)=C(O)C=2)O)=C1 LRBQNJMCXXYXIU-NRMVVENXSA-N 0.000 claims abstract description 47
- 229940033123 tannic acid Drugs 0.000 claims abstract description 47
- 235000015523 tannic acid Nutrition 0.000 claims abstract description 47
- 229920002258 tannic acid Polymers 0.000 claims abstract description 47
- 229910001428 transition metal ion Inorganic materials 0.000 claims abstract description 40
- 229910052742 iron Inorganic materials 0.000 claims abstract description 35
- 238000006243 chemical reaction Methods 0.000 claims abstract description 33
- 238000001027 hydrothermal synthesis Methods 0.000 claims abstract description 30
- 230000008569 process Effects 0.000 claims abstract description 27
- 238000005245 sintering Methods 0.000 claims abstract description 27
- 150000003623 transition metal compounds Chemical class 0.000 claims abstract description 20
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 17
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 17
- 239000002243 precursor Substances 0.000 claims abstract description 15
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 13
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 13
- 239000011574 phosphorus Substances 0.000 claims abstract description 13
- 239000013522 chelant Substances 0.000 claims abstract description 11
- 239000002904 solvent Substances 0.000 claims abstract description 7
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 19
- 229910001416 lithium ion Inorganic materials 0.000 claims description 19
- 239000007774 positive electrode material Substances 0.000 claims description 18
- -1 iron ions Chemical class 0.000 claims description 14
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 11
- 230000009920 chelation Effects 0.000 claims description 11
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 8
- 229910002651 NO3 Inorganic materials 0.000 claims description 6
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims description 6
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical compound [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 claims description 6
- IIPYXGDZVMZOAP-UHFFFAOYSA-N lithium nitrate Chemical compound [Li+].[O-][N+]([O-])=O IIPYXGDZVMZOAP-UHFFFAOYSA-N 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 6
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 claims description 5
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 4
- 238000001816 cooling Methods 0.000 claims description 4
- 230000000630 rising effect Effects 0.000 claims description 4
- CDVAIHNNWWJFJW-UHFFFAOYSA-N 3,5-diethoxycarbonyl-1,4-dihydrocollidine Chemical compound CCOC(=O)C1=C(C)NC(C)=C(C(=O)OCC)C1C CDVAIHNNWWJFJW-UHFFFAOYSA-N 0.000 claims description 3
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 claims description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 3
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 claims description 3
- 239000005955 Ferric phosphate Substances 0.000 claims description 3
- 229910021578 Iron(III) chloride Inorganic materials 0.000 claims description 3
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 3
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 claims description 3
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 claims description 3
- YNQRWVCLAIUHHI-UHFFFAOYSA-L dilithium;oxalate Chemical compound [Li+].[Li+].[O-]C(=O)C([O-])=O YNQRWVCLAIUHHI-UHFFFAOYSA-L 0.000 claims description 3
- 229940032958 ferric phosphate Drugs 0.000 claims description 3
- KTWOOEGAPBSYNW-UHFFFAOYSA-N ferrocene Chemical compound [Fe+2].C=1C=C[CH-]C=1.C=1C=C[CH-]C=1 KTWOOEGAPBSYNW-UHFFFAOYSA-N 0.000 claims description 3
- 229960002089 ferrous chloride Drugs 0.000 claims description 3
- 235000003891 ferrous sulphate Nutrition 0.000 claims description 3
- 239000011790 ferrous sulphate Substances 0.000 claims description 3
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 claims description 3
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 claims description 3
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims description 3
- RUTXIHLAWFEWGM-UHFFFAOYSA-H iron(3+) sulfate Chemical compound [Fe+3].[Fe+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O RUTXIHLAWFEWGM-UHFFFAOYSA-H 0.000 claims description 3
- 229910000359 iron(II) sulfate Inorganic materials 0.000 claims description 3
- 229910000399 iron(III) phosphate Inorganic materials 0.000 claims description 3
- 229910000360 iron(III) sulfate Inorganic materials 0.000 claims description 3
- XIXADJRWDQXREU-UHFFFAOYSA-M lithium acetate Chemical compound [Li+].CC([O-])=O XIXADJRWDQXREU-UHFFFAOYSA-M 0.000 claims description 3
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 3
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 3
- INHCSSUBVCNVSK-UHFFFAOYSA-L lithium sulfate Inorganic materials [Li+].[Li+].[O-]S([O-])(=O)=O INHCSSUBVCNVSK-UHFFFAOYSA-L 0.000 claims description 3
- MCVFFRWZNYZUIJ-UHFFFAOYSA-M lithium;trifluoromethanesulfonate Chemical compound [Li+].[O-]S(=O)(=O)C(F)(F)F MCVFFRWZNYZUIJ-UHFFFAOYSA-M 0.000 claims description 3
- 235000019837 monoammonium phosphate Nutrition 0.000 claims description 3
- 239000006012 monoammonium phosphate Substances 0.000 claims description 3
- 150000003839 salts Chemical class 0.000 claims description 3
- RBTVSNLYYIMMKS-UHFFFAOYSA-N tert-butyl 3-aminoazetidine-1-carboxylate;hydrochloride Chemical compound Cl.CC(C)(C)OC(=O)N1CC(N)C1 RBTVSNLYYIMMKS-UHFFFAOYSA-N 0.000 claims description 3
- ITMCEJHCFYSIIV-UHFFFAOYSA-M triflate Chemical compound [O-]S(=O)(=O)C(F)(F)F ITMCEJHCFYSIIV-UHFFFAOYSA-M 0.000 claims description 3
- 238000004321 preservation Methods 0.000 claims description 2
- 238000004378 air conditioning Methods 0.000 claims 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 28
- 229910052799 carbon Inorganic materials 0.000 abstract description 27
- 239000010405 anode material Substances 0.000 abstract description 24
- 239000011247 coating layer Substances 0.000 abstract description 8
- 239000013078 crystal Substances 0.000 description 22
- 150000002500 ions Chemical class 0.000 description 17
- 239000000463 material Substances 0.000 description 17
- 239000010936 titanium Substances 0.000 description 13
- 238000009792 diffusion process Methods 0.000 description 11
- 239000011248 coating agent Substances 0.000 description 8
- 238000000576 coating method Methods 0.000 description 8
- 230000000694 effects Effects 0.000 description 8
- 239000007772 electrode material Substances 0.000 description 7
- 230000035484 reaction time Effects 0.000 description 7
- 239000010410 layer Substances 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 239000002245 particle Substances 0.000 description 5
- 239000012071 phase Substances 0.000 description 5
- 229910010707 LiFePO 4 Inorganic materials 0.000 description 4
- LCKIEQZJEYYRIY-UHFFFAOYSA-N Titanium ion Chemical compound [Ti+4] LCKIEQZJEYYRIY-UHFFFAOYSA-N 0.000 description 4
- 238000005054 agglomeration Methods 0.000 description 4
- 230000002776 aggregation Effects 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 4
- 238000003763 carbonization Methods 0.000 description 4
- 239000010406 cathode material Substances 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 239000003792 electrolyte Substances 0.000 description 4
- 238000004146 energy storage Methods 0.000 description 4
- 239000012535 impurity Substances 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 238000007600 charging Methods 0.000 description 3
- 125000004122 cyclic group Chemical group 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 238000007599 discharging Methods 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 238000003760 magnetic stirring Methods 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 238000007670 refining Methods 0.000 description 3
- 239000011163 secondary particle Substances 0.000 description 3
- 239000002356 single layer Substances 0.000 description 3
- 238000006467 substitution reaction Methods 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 238000005406 washing Methods 0.000 description 3
- CIWBSHSKHKDKBQ-JLAZNSOCSA-N Ascorbic acid Chemical compound OC[C@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-JLAZNSOCSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 229910011570 LiFe 1-x Inorganic materials 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 230000004888 barrier function Effects 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 238000010277 constant-current charging Methods 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 229910000398 iron phosphate Inorganic materials 0.000 description 2
- SNKMVYBWZDHJHE-UHFFFAOYSA-M lithium;dihydrogen phosphate Chemical compound [Li+].OP(O)([O-])=O SNKMVYBWZDHJHE-UHFFFAOYSA-M 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 230000029219 regulation of pH Effects 0.000 description 2
- 238000004904 shortening Methods 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- 229910052723 transition metal Inorganic materials 0.000 description 2
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 1
- 229910011893 LiFe0.9Ti0.1PO4 Inorganic materials 0.000 description 1
- 229910010710 LiFePO Inorganic materials 0.000 description 1
- 229910015643 LiMn 2 O 4 Inorganic materials 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 229910052581 Si3N4 Inorganic materials 0.000 description 1
- 238000003917 TEM image Methods 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 229910003481 amorphous carbon Inorganic materials 0.000 description 1
- 229960005070 ascorbic acid Drugs 0.000 description 1
- 235000010323 ascorbic acid Nutrition 0.000 description 1
- 239000011668 ascorbic acid Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000013590 bulk material Substances 0.000 description 1
- OJIJEKBXJYRIBZ-UHFFFAOYSA-N cadmium nickel Chemical compound [Ni].[Cd] OJIJEKBXJYRIBZ-UHFFFAOYSA-N 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 230000000536 complexating effect Effects 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000011066 ex-situ storage Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 1
- 229910001386 lithium phosphate Inorganic materials 0.000 description 1
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 1
- 230000003446 memory effect Effects 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000007709 nanocrystallization Methods 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 239000010450 olivine Substances 0.000 description 1
- 229910052609 olivine Inorganic materials 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 125000002467 phosphate group Chemical group [H]OP(=O)(O[H])O[*] 0.000 description 1
- 229920001690 polydopamine Polymers 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000003746 solid phase reaction Methods 0.000 description 1
- 229910052596 spinel Inorganic materials 0.000 description 1
- 239000011029 spinel Substances 0.000 description 1
- 239000011232 storage material Substances 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- 150000003624 transition metals Chemical class 0.000 description 1
- TWQULNDIKKJZPH-UHFFFAOYSA-K trilithium;phosphate Chemical compound [Li+].[Li+].[Li+].[O-]P([O-])([O-])=O TWQULNDIKKJZPH-UHFFFAOYSA-K 0.000 description 1
- 238000001132 ultrasonic dispersion Methods 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
The invention provides core-shell carbon-coated doped lithium iron phosphate, a preparation method and application thereof. The preparation method comprises the following steps: in the presence of a first solvent, chelating the iron source compound, the transition metal compound and tannic acid to obtain a chelate-containing product system, wherein the valence state of transition metal ions in the transition metal compound is more than or equal to 4; carrying out hydrothermal synthesis reaction on a phosphorus source compound, a lithium source compound and a chelate to obtain a tannic acid coated transition metal ion doped lithium iron phosphate precursor; and sintering the tannic acid coated transition metal ion doped lithium iron phosphate precursor in an inert atmosphere to obtain the core-shell carbon coated doped lithium iron phosphate. The core-shell carbon-coated doped lithium iron phosphate prepared by the method has the advantages of low cost, good uniformity and compactness of a carbon coating layer, small grain size and the like, so that the prepared anode material can obtain better multiplying power performance and dynamics performance in the application process.
Description
Technical Field
The invention relates to the manufacture of lithium iron phosphate type lithium ion batteries, in particular to core-shell carbon coated doped lithium iron phosphate, a preparation method and application thereof.
Background
Compared with the commercialized rechargeable secondary batteries such as nickel-cadmium batteries, lead-acid batteries and the like, the lithium ion battery has the advantages of high energy density, high power density, long service life, no memory effect and the like, has been widely applied to various portable electronic devices, and has been gradually applied to new energy automobile energy storage systems. The existing lithium ion power battery can not meet the energy storage requirement of us, and development of a lithium ion battery energy storage material with higher performance is needed, wherein the development of a lithium ion power battery anode material is critical. At present lithium ionThe study of the positive electrode material of the sub-battery is mainly focused on layered lithium cobalt oxide LiCoO 2 Material (LCO), spinel lithium manganate LiMn 2 O 4 Material (LMO), olivine lithium iron phosphate LiFePO 4 (LFP) and layered ternary material systems, etc. As positive electrode materials, they are each advantageous in that cobalt in a raw material of lithium cobaltate is expensive and also toxic; the high-temperature performance and the long-cycle performance of lithium manganate are obviously insufficient, and still further optimization is needed; layered ternary systems, particularly high nickel systems, although providing high energy densities, are inherently moisture sensitive and poorly thermally stable. The lithium iron phosphate has rich resources, low cost, environmental protection, stable crystal structure, good safety performance and higher theoretical capacity (-170 mAh.g) -1 ) And the like, and has wide application value in lithium ion power batteries. However, based on LiFePO 4 Crystal structure can be seen with FeO 6 Octahedron and PO 4 Co-angular connection of tetrahedra and FeO 6 Octahedral quilt PO of (2) 4 Tetrahedral separation, which is during charge and discharge, li + Is limited to one-dimensional channel diffusion, so that LiFePO 4 Exhibits low electron conductivity and ion diffusion coefficient at room temperature, and thus exhibits poor rate performance and severe capacity fade in long cycles in practical applications.
For LiFePO as described above 4 The disadvantages of lower electron conductivity and ion diffusion rate of materials have been proposed by researchers to modify the materials in a number of ways, mainly into the following categories: 1. the particle nanocrystallization reduces the particle size of lithium iron phosphate, and can effectively shorten Li + Thereby improving the diffusion rate and the multiplying power performance of the diffusion path; 2. after ion doping and ion doping with different particle sizes, one of the ion doped silicon nitride can manufacture lattice defects, widen ion diffusion channels and reduce Li + A diffusion energy barrier, wherein the second energy gap width can be reduced to a certain extent, so that the electron conductivity of the bulk material is improved; 3. the morphology is controlled, the special morphology structure can lead the material to be fully contacted with electrolyte, increase the electrochemical active site of the material, and control the growth direction of crystal to Li + Crystal plane progression of diffusion channelPreferred orientation, ensure Li + Fast insertion of electrons and efficient conduction of electrons; 4. the conductive carbon is compounded/coated, the electron conductivity of the material can be obviously improved by adding the coated carbon, the charge and discharge performance of the battery under a high multiplying power is improved, meanwhile, the coated carbon can limit the growth of crystal grains to a certain extent, an effective electron and ion transmission channel is provided, the electrolyte can be absorbed by the porous structure of the coated carbon, more electrochemical active sites can be realized by increasing the contact area of the electrolyte, and therefore, excellent and stable electrochemical performance can be continuously output.
The current state of the art for carbon coated lithium iron phosphate materials is as follows:
the prior literature provides a preparation method of lithium iron phosphate with a carbon-coated hierarchical structure, which is characterized in that the lithium iron phosphate with the hierarchical structure is obtained through a one-step hydrothermal synthesis method, and the synthesized lithium iron phosphate is fully mixed with a carbon source in a subsequent sintering process to prepare the lithium iron phosphate with the carbon-coated hierarchical structure, so that the lithium iron phosphate with the hierarchical structure has high specific capacity and good cycle performance. However, this method has the disadvantages: the organic carbon sources available for coating lithium iron phosphate are limited in choice and some of them are expensive, such as ascorbic acid, polydopamine, etc.
Another prior document provides a hydrothermal preparation method of nano lithium iron phosphate, which synthesizes a lithium iron phosphate material with small particle size (100 nm) and good uniformity by adding an organic compound with a phosphate end group, and mixes the material with an organic carbon source in a subsequent high-temperature sintering process to prepare nano lithium iron phosphate with carbon coating, but the waste water containing additives is difficult to treat in the preparation process. However, this method has the disadvantages: the coated amorphous carbon is not uniform in thickness and the coating may not be dense.
Still another prior document provides a method for preparing lithium iron phosphate by mixing phosphoric acid, an iron source and a PH buffer, performing a hydrothermal reaction to prepare an iron phosphate precursor, and then mixing and sintering the iron phosphate precursor with a lithium source and a carbon source to obtain lithium iron phosphate, and finally obtaining lithium iron phosphate in a single phase, wherein the lithium iron phosphate is used as a positive electrode material of a lithium ion battery, so that the battery has excellent cycle performance and excellent rate performance. However, this method has the disadvantages: in the long-time high-temperature carbonization process, the nano-scale lithium iron phosphate coated by the ex-situ carbon can be agglomerated into large secondary particle lithium iron phosphate positive electrode material, and the diffusion kinetics of lithium ions is slow.
In view of the above, there is a need to provide a new method for preparing lithium iron phosphate.
Disclosure of Invention
The invention mainly aims to provide core-shell carbon coated doped lithium iron phosphate, and a preparation method and application thereof, so as to solve the problems of high cost, uneven and non-compact coating of a carbon layer, easy agglomeration of crystal grains and the like of the conventional lithium iron phosphate anode material.
In order to achieve the above object, according to one aspect of the present invention, there is provided a method for preparing core-shell carbon-coated doped lithium iron phosphate, the method comprising: in the presence of a first solvent, chelating the iron source compound, the transition metal compound and tannic acid to obtain a chelate-containing product system, wherein the valence state of transition metal ions in the transition metal compound is more than or equal to 4; carrying out hydrothermal synthesis reaction on a phosphorus source compound, a lithium source compound and a chelate to obtain a tannic acid coated transition metal ion doped lithium iron phosphate precursor; and sintering the tannic acid coated transition metal ion doped lithium iron phosphate precursor in an inert atmosphere to obtain the core-shell carbon coated doped lithium iron phosphate.
Further, the transition metal ion is selected from Ti 4+ 、W 6+ 、Ta 5+ 、Nb 5+ 、Zr 4+ 、Mo 6+ And V 5+ One or more of the group consisting of, preferably, ti 4+ The method comprises the steps of carrying out a first treatment on the surface of the The transition metal compound is one or more of chloride, sulfate, nitrate, acetate and organic salt of transition metal ion.
Further, in the chelation reaction, the molar ratio of the iron ions to the transition metal ions in the tannic acid and the iron source compound is (0.1 to 3): 1: (0.001-0.02).
Further, the molar ratio (1 to 4) of the transition metal ion to the phosphorus source compound in the lithium source compound, the iron source compound, and the transition metal compound: (0.9-1.5): (0.001-0.02): (0.6-1.5).
Further, the temperature of the hydrothermal synthesis reaction is 120-240 ℃, the reaction time is 5-48 h, and the pH is 5-8.
Further, the sintering temperature in the sintering process is 350-900 ℃, and the heat preservation time is 3-12 hours;
the temperature rising rate in the sintering process is 2-10 ℃ min -1 Preferably 5℃min -1 The cooling rate after sintering is 2-15 ℃ min -1 Preferably at 10℃min -1 。
Further, the iron source compound is selected from one or more of ferrous chloride, ferrous sulfate, ferrous nitrate, ferric chloride, ferric sulfate, ferric nitrate, ferric phosphate, ferric acetylacetonate, ferric trifluoromethane sulfonate and ferrocene; the phosphorus source compound is selected from one or more of phosphoric acid, monoammonium phosphate and lithium dihydrogen phosphate; and the lithium source compound is selected from one or more of the group consisting of lithium carbonate, lithium hydroxide, lithium sulfate, lithium acetate, lithium nitrate, lithium trifluoromethane sulfonate, and lithium oxalate.
The second aspect of the present application also provides a core-shell carbon-coated doped lithium iron phosphate, which is prepared by the preparation method provided by the present application, preferably, the core-shell carbon-coated doped lithium iron phosphate can adopt LiFe 1-x M x PO 4 And @ C, wherein x is 0.001-0.02, and M is a transition metal ion with a valence of 4 or more.
A third aspect of the present application also provides a lithium ion battery comprising a positive electrode material comprising the core-shell carbon-coated doped lithium iron phosphate of claim 8.
A fourth aspect of the present application also provides an electric drive comprising the lithium ion battery of claim 9.
By adopting the technical scheme of the invention, the risk that transition metal ions cannot enter the lithium iron phosphate crystal lattice due to loss of transition metal ions in the treatment processes of washing and the like can be effectively inhibited through the chelation reaction, and the risk can be effectively reducedThe iron ions are precipitated in the subsequent pH regulation and control, so that the distribution uniformity of each component is improved. Through hydrothermal synthesis reaction and sintering process, the tannic acid can be carbonized into a single-layer or multi-layer carbon coating layer with uniform thickness on the surface of lithium iron phosphate after carbonization, which is beneficial to remarkably improving the electronic conductivity of the positive electrode material and optimizing the dynamic performance of the electrode material; at the same time, the growth of crystal grains is limited in the carbonization process of tannic acid, and the agglomeration of secondary particles is restrained, thereby achieving the purposes of refining the grain size and shortening Li + To improve Li + The transport rate is increased, so that the rate capability of the electrode material is greatly improved. In addition, tannic acid is adopted as an organic carbon source, and the source of the raw material is wide and the cost is low, so that the production cost of the lithium iron phosphate anode material can be greatly reduced. On the basis, the core-shell carbon-coated doped lithium iron phosphate prepared by the method has the advantages of low cost, good uniformity and compactness of a carbon coating layer, small grain size and the like, so that the prepared anode material can obtain better multiplying power performance and dynamic performance in the application process.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. In the drawings:
FIG. 1 is an XRD pattern of a core-shell carbon-coated nanoscale titanium-doped lithium iron phosphate positive electrode material prepared in example 1;
FIG. 2 is an SEM image of a core-shell carbon-coated nanoscale titanium-doped lithium iron phosphate positive electrode material prepared in example 1;
FIG. 3 is a TEM image of the core-shell carbon-coated nanoscale titanium-doped lithium iron phosphate positive electrode material prepared in example 1;
fig. 4 is a charge-discharge curve of the core-shell carbon-coated nanoscale titanium-doped lithium iron phosphate cathode material prepared in example 1.
Detailed Description
It should be noted that, in the case of no conflict, the embodiments and features in the embodiments may be combined with each other. The present invention will be described in detail with reference to examples.
As described in the background art, the existing lithium iron phosphate anode material has the problems of high cost, uneven and compact coating of a carbon layer, easy agglomeration of crystal grains and the like. In order to solve the technical problems, the application provides a preparation method of core-shell carbon-coated doped lithium iron phosphate, which comprises the following steps: in the presence of a first solvent, chelating the iron source compound, the transition metal compound and tannic acid to obtain a chelate-containing product system, wherein the valence state of transition metal ions in the transition metal compound is more than or equal to 4; carrying out hydrothermal synthesis reaction on a phosphorus source compound, a lithium source compound and a chelate to obtain a tannic acid coated transition metal ion doped lithium iron phosphate precursor; and sintering the tannic acid coated transition metal ion doped lithium iron phosphate precursor in an inert atmosphere to obtain the core-shell carbon coated doped lithium iron phosphate.
Before the hydrothermal synthesis stage, tannic acid is subjected to chelation reaction with iron ions in the iron source compound and high-valence transition metal ions in the transition metal compound preferentially to form a cyclic chelate; then in the hydrothermal synthesis process, the cyclic chelate reacts with a lithium source compound and a phosphorus source compound to generate high-valence transition metal doped lithium iron phosphate crystal nucleus, and tannic acid uniformly grows on the outer surface of the crystal nucleus to form a core-shell nanoscale lithium iron phosphate structure (precursor). In the high-temperature solid-phase reaction process (sintering process), tannic acid is carbonized into a single-layer or multi-layer carbon coating layer with uniform thickness on the surface of lithium iron phosphate, so that the required core-shell carbon coating doped lithium iron phosphate is obtained.
The chelating reaction can effectively inhibit the risk that transition metal ions cannot enter the lithium iron phosphate crystal lattice due to loss in the treatment process of washing and the like, and can effectively reduce precipitation of the iron ions in the subsequent pH regulation, so that the distribution uniformity of each component is improved. Through hydrothermal synthesis reaction and sintering process, tannic acid can be carbonized into single-layer or multi-layer carbon bags with uniform thickness on the surface of lithium iron phosphate after carbonizationThe coating is beneficial to remarkably improving the electron conductivity of the positive electrode material and optimizing the dynamic performance of the electrode material; at the same time, the growth of crystal grains is limited in the carbonization process of tannic acid, and the agglomeration of secondary particles is restrained, thereby achieving the purposes of refining the grain size and shortening Li + To improve Li + The transport rate is increased, so that the rate capability of the electrode material is greatly improved. In addition, tannic acid is adopted as an organic carbon source, and the source of the raw material is wide and the cost is low, so that the production cost of the lithium iron phosphate anode material can be greatly reduced. On the basis, the core-shell carbon-coated doped lithium iron phosphate prepared by the method has the advantages of low cost, good uniformity and compactness of a carbon coating layer, small grain size and the like, so that the prepared anode material can obtain better multiplying power performance and dynamic performance in the application process.
Since tannic acid is solid, it is necessary to dissolve tannic acid in a first solvent (such as water) to form a solution a before the tannic acid is subjected to the chelation reaction. Preferably, the above-described dissolution process may be performed under magnetic stirring in order to increase the dissolution rate thereof. Meanwhile, in order to improve the chelating effect of the solution A and other components (the iron source compound and the transition metal compound), an ultrasonic device can be adopted for dispersion, and whether magnetic stirring is carried out or not is selected according to the situation. In another embodiment, after solution a is formulated, the iron source compound and the transition metal compound are mixed with a second solvent (such as water) to form solution B. Solution a and solution B are then mixed to effect the chelation reaction.
The "inert atmosphere" means a gas that does not react with the reaction raw material, such as nitrogen, inert gas, or the like.
In the hydrothermal synthesis stage, transition metal ions can enter lithium iron phosphate crystal lattice to manufacture crystal lattice defects, widen ion diffusion channels and reduce Li + Diffusion energy barrier, thereby playing an effect of improving the electron conductivity of the positive electrode material. In a preferred embodiment, the transition metal ions include, but are not limited to, ti 4+ 、W 6+ 、Ta 5+ 、Nb 5+ 、Zr 4+ 、Mo 6+ And V 5+ One or more of the group consisting of, preferably, ti 4+ The method comprises the steps of carrying out a first treatment on the surface of the The transition metal compound is one or more of chloride, sulfate, nitrate, acetate and organic salt of transition metal ion. Compared with other high-valence transition metal ions, the iron ions and the tannic acid have better binding performance, so that the utilization rate of the transition metal ions is further improved, the distribution uniformity of each component in the anode material is improved, and the electrical performance of the anode material is more uniform. More preferably, in the chelation reaction, the molar ratio of tannic acid, iron ions in the iron source compound, and transition metal ions is (0.1 to 3): 1: (0.001-0.02).
In a preferred embodiment, the ratio of the moles of transition metal ion to the moles of phosphorus source compound in the lithium source compound, the iron source compound, and the transition metal compound (1 to 4): (0.9-1.5): (0.001-0.02): (0.6-1.5). The molar ratio of the lithium source compound, the iron source compound, the transition metal compound and the phosphorus source compound includes but is not limited to the above range, and the limitation of the molar ratio in the above range is beneficial to reducing the generation of impurity phases, better controlling the growth of crystal grains and improving the energy density and the specific discharge capacity of the lithium iron phosphate material in the application process.
The precursor material of the lithium iron phosphate can be obtained through hydrothermal synthesis reaction. In a preferred embodiment, the hydrothermal synthesis reaction is carried out at a temperature of 120 to 240℃for a reaction time of 5 to 48 hours and at a pH of 5 to 8. The temperature, reaction time and pH of the hydrothermal synthesis reaction are not limited to the above ranges, but are limited to the above ranges, which is favorable for further reducing the generation of impurity phases, improving the crystallinity and refining grains, thereby being favorable for further improving the electrochemical performance of the lithium iron phosphate material prepared subsequently.
In a preferred embodiment, the sintering temperature of the sintering process is 350-900 ℃ and the holding time is 3-12 h. The sintering process temperature and holding time include, but are not limited to, the above ranges, and limiting the above ranges is beneficial to further improving the compaction density and further improving the electrochemical comprehensive performance. In order to further improve the electrochemical comprehensive performance, it is more preferable thatThe temperature rising rate in the sintering process is 2-10 ℃ min -1 Preferably 5℃min -1 The method comprises the steps of carrying out a first treatment on the surface of the The cooling rate after sintering is 2-15 ℃ min -1 Preferably at 10℃min -1 。
The iron source compound, phosphorus source compound and lithium source compound used in the present application may be of the types commonly used in the art. In a preferred embodiment, the iron source compound includes, but is not limited to, one or more of the group consisting of ferrous chloride, ferrous sulfate, ferrous nitrate, ferric chloride, ferric sulfate, ferric nitrate, ferric phosphate, ferric acetylacetonate, ferric trifluoromethane sulfonate, ferrocene; phosphorus source compounds include, but are not limited to, one or more of the group consisting of phosphoric acid, monoammonium phosphate, lithium dihydrogen phosphate; and lithium source compounds including, but not limited to, one or more of the group consisting of lithium carbonate, lithium hydroxide, lithium sulfate, lithium acetate, lithium nitrate, lithium trifluoromethane sulfonate, and lithium oxalate.
The second aspect of the application also provides a core-shell carbon-coated doped lithium iron phosphate, which is prepared by adopting the preparation method provided by the application. The core-shell carbon-coated doped lithium iron phosphate prepared by the method has the advantages of low cost, good uniformity and compactness of a carbon coating layer, small grain size and the like. In order to further improve the comprehensive performance, preferably, the core-shell carbon-coated doped lithium iron phosphate can adopt LiFe 1-x M x PO 4 And @ C, wherein x is 0.001-0.02, and M is a transition metal ion with a valence of 4 or more.
Preferably, as the positive electrode material of the lithium ion battery, the first charge gram capacity is 164 mAh.g under the current density of 0.1C -1 The coulomb efficiency of the first circle can reach 98 percent. At a current density of 1C, after 3000 cycles, the capacity retention was 97%. Has higher electrochemical capacity and excellent cycling stability.
The third aspect provided herein also provides a lithium ion battery comprising a positive electrode material comprising the core-shell carbon-coated doped lithium iron phosphate provided herein. The core-shell carbon-coated doped lithium iron phosphate prepared by the method has the advantages of low cost, good uniformity and compactness of a carbon coating layer, small grain size and the like, so that the prepared anode material can be used as an anode of a lithium ion battery to greatly improve the rate performance and the dynamic performance of the lithium ion battery.
The fourth aspect that this application provided still provides an electric drive device, and electric drive device includes the lithium ion battery that this application provided. The lithium ion battery containing the core-shell carbon-coated doped lithium iron phosphate is used as an energy module of an electric driving device, so that the advantages of energy storage, cruising ability and environmental protection can be greatly improved.
The present application is described in further detail below in conjunction with specific embodiments, which should not be construed as limiting the scope of the claims.
Example 1
The preparation method of the core-shell carbon-coated nanoscale titanium-doped lithium iron phosphate anode material in the embodiment specifically comprises the following steps:
tannic Acid (TA) was mixed with deionized water to form solution a, wherein the TA content in solution a was 2.5wt.%.
FeCl is added 3 And TiCl 4 Adding the solution A, performing ultrasonic dispersion for 1h, and performing magnetic stirring at room temperature for 2-6 h, wherein the time is enough for complexing tannic acid with transition metal iron ions and titanium ions to form a cyclic chelate.
LiOH and NH 4 H 2 PO 4 And mixing with deionized water to obtain a solution B. According to tannic acid, liOH and FeCl 3 、TiCl 4 And NH 4 H 2 PO 4 The molar ratio of the solution A to the solution B is 1.5:1.4:1.0:0.005:1.3, the solution A and the solution B are stirred uniformly and then transferred into a hydrothermal reaction kettle, the PH value of the solution is regulated to be 6.5-7.5, and the hydrothermal synthesis reaction is carried out at 180 ℃ for 18h. And then washing, filtering and drying to obtain the tannic acid coated lithium iron phosphate precursor.
Placing tannic acid coated lithium iron phosphate precursor into a tube furnace, and adding the tannic acid coated lithium iron phosphate precursor into N 2 Or sintering in Ar or other protective atmosphere at 850 deg.c for 10 hr to obtain LiFe 0.99 Ti 0.01 PO 4 And @ C. XRD patterns, SEM patterns and TEM patterns of the core-shell carbon coated nanoscale titanium doped lithium iron phosphate cathode material prepared in the embodiment 1 are sequentially shown in figures 1, 2 and 3.
Example 2
The differences from example 1 are: the TA content in solution a was 0.5wt.%, the other steps being the same as in example 1.
Example 3
The differences from example 1 are: the TA content in solution a was 1.5wt.%, the other steps being the same as in example 1.
Example 4
The differences from example 1 are: the TA content in solution a was 5wt.%, and the other steps were the same as in example 1.
Example 5
The differences from example 1 are: the temperature of the hydrothermal synthesis reaction was 200℃and the other steps were the same as in example 1.
Example 6
The differences from example 1 are: the temperature of the hydrothermal synthesis reaction was 220℃and the other steps were the same as in example 1.
Example 7
The differences from example 1 are: the hydrothermal synthesis reaction time was 6 hours, and the other steps were the same as in example 1.
Example 8
The differences from example 1 are: the hydrothermal synthesis reaction time was 12 hours, and the other steps were the same as in example 1.
Example 9
The differences from example 1 are: substitution of transition metal compounds for equimolar amounts of V 5+ The other steps were the same as in example 1. The core-shell carbon-coated nanoscale vanadium-doped lithium iron phosphate anode material is LiFe 0.99 V 0.01 PO 4 @C。
Example 10
The differences from example 1 are: substitution of transition metal compounds for equimolar amounts of Nb 5+ The other steps were the same as in example 1. The core-shell carbon-coated nanoscale niobium-doped lithium iron phosphate anode material is LiFe 0.99 Nb .01 PO 4 @C。
Example 11
The differences from example 1 are: substitution of transition metal compounds for equimolar amounts of Ta 5+ The other steps were the same as in example 1. The core-shell carbon-coated nanoscale tantalum-doped lithium iron phosphate anode material is LiFe 0.99 Ta 0.01 PO 4 @C。
Example 12
The differences from example 1 are: the differences from example 1 are: the hydrothermal synthesis reaction was carried out at 120℃for 48 hours, and the other steps were the same as in example 1. The core-shell carbon-coated nanoscale titanium-doped lithium iron phosphate anode material is LiFe 0.99 Ti 0.01 PO 4 @C。
Example 13
The differences from example 1 are: the hydrothermal synthesis reaction was carried out at 240℃for 5 hours, and the other steps were the same as in example 1.
Example 14
The differences from example 1 are: the temperature of the hydrothermal synthesis reaction was 140℃and the other steps were the same as in example 1.
Example 15
The differences from example 1 are: the temperature of the hydrothermal synthesis reaction was 160℃and the other steps were the same as in example 1.
Example 16
The differences from example 1 are: the temperature of the hydrothermal synthesis reaction was 100℃and the other steps were the same as in example 1.
Example 17
The differences from example 1 are: liOH, feCl 3 、TiCl 4 And NH 4 H 2 PO 4 The molar ratio of (2) was 1.4:1.0:0.001:1.3, and the other steps were the same as in example 1. The core-shell carbon-coated nanoscale titanium-doped lithium iron phosphate anode material is LiFe 0.999 Ti 0.001 PO 4 @C。
Example 18
The differences from example 1 are: liOH, feCl 3 、TiCl 4 And NH 4 H 2 PO 4 The molar ratio of (2) was 1.4:1.0:0.01:1.3, the other steps are the same as in example 1. The core-shell carbon-coated nanoscale titanium-doped lithium iron phosphate anode material is LiFe 0.99 Ti 0.01 PO 4 @C。
Example 19
The differences from example 1 are: liOH, feCl 3 、TiCl 4 And NH 4 H 2 PO 4 The molar ratio of (2) was 1.4:1.0:0.015:1.3, and the other steps were the same as in example 1. The core-shell carbon-coated nanoscale titanium-doped lithium iron phosphate anode material is LiFe 0.985 Ti 0.015 PO 4 @C。
Example 20
The differences from example 1 are: liOH, feCl 3 、TiCl 4 And NH 4 H 2 PO 4 The molar ratio of (2) was 1.4:1.0:0.02:1.3, and the other steps were the same as in example 1. The core-shell carbon-coated nanoscale titanium-doped lithium iron phosphate anode material is LiFe 0.98 Ti 0.02 PO 4 @C。
Example 21
The differences from example 1 are: liOH, feCl 3 、TiCl 4 And NH 4 H 2 PO 4 The molar ratio of (2) was 1.4:1.0:0.04:1.3, and the other steps were the same as in example 1. The core-shell carbon-coated nanoscale titanium-doped lithium iron phosphate anode material is LiFe 0.96 Ti 0.04 PO 4 @C。
Example 22
The differences from example 1 are: in the chelation reaction, the molar ratio of iron ions to transition metal ions in tannic acid and the iron source compound was 0.1:1:0.02, and the other steps were the same as in example 1. The core-shell carbon-coated nanoscale titanium-doped lithium iron phosphate anode material is LiFe 0.98 Ti 0.02 PO 4 @C。
Example 23
The differences from example 1 are: in the chelation reaction, the molar ratio of iron ions to transition metal ions in tannic acid and the iron source compound was 3:1:0.001, and the other steps were the same as in example 1. The core-shell carbon-coated nanoscale titanium-doped lithium iron phosphate anode material is LiFe 0.999 Ti 0.001 PO 4 @C。
Example 24
The differences from example 1 are: in the chelation reaction, the molar ratio of iron ions to transition metal ions in tannic acid and the iron source compound was 0.5:1:0.1, and the other steps were the same as in example 1. The core-shell carbon-coated nanoscale titanium-doped lithium iron phosphate anode material is LiFe 0.9 Ti 0.1 PO 4 @C。
Comparative example 1
The present comparative example uses a transition metal ion doped lithium iron phosphate material without any coating treatment.
Performance test:
the materials prepared in examples 1 to 24 and comparative example 1 were tested for electrochemical performance using a CR2032 type button cell, one of which was a mixture (weight ratio of 97:1.5:1.5) of the prepared core-shell carbon-coated nanoscale lithium iron phosphate positive electrode material, acetylene black, polyvinylidene fluoride, the other of which was a metallic lithium sheet, and the electrolyte was 1mol/L LiPF 6 Dissolved in a solvent of EC/DMC/EMC (volume ratio 1:1:1). The constant current charge-discharge voltage range is 2.0-3.7V.
1) Gram capacity for first discharge and coulombic efficiency test for first time:
after the button cell is assembled, (1) charging: constant current charging is carried out to 3.7V at 0.1C, and the specific charge capacity is recorded as Q1; (2) discharging: constant current of 0.1C is discharged to 2V, and the specific discharge capacity is recorded as Q2; first coulombic efficiency is abbreviated as ICE, ice=q2/Q1.
2) And (3) testing the cycle performance:
(1) charging: constant current charging is carried out on 1C until the voltage reaches 3.7V, and the interval is 10min; (2) discharging: constant current of 1C is put to 2V for 10min; (3) repeating (1) and (2) 3000 circles; the capacity retention ratio is abbreviated CR.
3) And (3) multiplying power performance test:
(1) charging 0.1C constant current to 3.7V, and discharging 0.1C constant current to 2V after 10min interval; (2) repeating the process (1) for 10 circles; (3) the current density in "(1), (2)" was raised to 1C, 3C and 10C, wherein the discharge capacities corresponding to 1C, 3C and 10C were Q3, Q4, Q5 and Q6, respectively. The test results are shown in Table 1. Fig. 4 is a charge-discharge curve of the core-shell carbon-coated nanoscale titanium-doped lithium iron phosphate cathode material prepared in example 1 and the cathode material in comparative example 1.
TABLE 1
From the data in table 1, when the content of tannic acid was increased appropriately, the first charge capacity, cycle performance and rate of the sample were significantly improved; when the content of tannic acid is excessively increased, the cycle performance and the rate performance of the tannic acid are reduced to a certain extent. Because the content of tannic acid in the solution is increased, the carbon coating layer on the surface of the lithium iron phosphate crystal grain is thickened, the thicker carbon layer can obstruct the transmission of lithium ions, and meanwhile, the specific capacity of the whole material can be reduced.
From examples 1, 5, 6, 12 to 16, increasing the hydrothermal temperature resulted in some decrease in the cycle performance and rate performance of the electrode material, mainly because the increase in the hydrothermal temperature increased the probability of collision of crystals during the nucleation period of crystals, and thus large particles were liable to grow. Too low a hydrothermal temperature may result in the presence of a portion of the lithium phosphate impurity phase in the product that may deteriorate the electrochemical properties of the electrode material. In addition, from examples 12 and 13, it is important to select a proper hydrothermal reaction temperature, and it is not possible to lengthen or shorten the hydrothermal reaction time.
From examples 1, 7 and 8, the shorter hydrothermal time has a great influence on electrochemical properties, and it can be ascribed to incomplete crystal formation due to the excessively short reaction time.
From examples 1, 9, 10 and 11, the electrochemical properties of the lithium iron phosphate electrode materials doped with different metal ions in the +5 valence state are significantly inferior to those of Ti +4 The electrochemical performance of the ion doped lithium iron phosphate positive electrode material shows that while the selection of the doped ions with higher valence state or larger ionic radius can increase the defects of the lithium iron phosphate crystal lattice and optimize the electrochemical performance, the selection of the doped ions with higher valence state or larger ionic radius can cause the doped ions to be difficult to enter the crystal lattice of the lithium iron phosphate, thereby not achieving the effect of ion doping, the electrochemical performance of the ion doped lithium iron phosphate positive electrode material is characterized in thatThe effect of optimizing doping ions of higher valence states or larger ionic radii to improve the electrochemical performance of lithium iron phosphate anodes requires exploration of suitable ion doping levels.
From examples 1 and 17 to 21, ti 4+ The choice of the amount of ion doping will also have an effect on the electrochemical properties of the product. Too low titanium ion doping content, on the contrary, cannot play the effect of titanium ion doping; the effect of improving the electrochemical performance is not obvious due to the slightly excessive titanium ion doping amount; higher titanium ion doping levels can instead result in small amounts of impurity phases in the product.
From examples 1, 22 to 24, limiting the molar ratio of iron ions to transition metal ions in tannic acid, iron source compounds in the chelation reaction to within the preferred ranges of the present application is advantageous for improving the electrochemical performance of core-shell carbon-coated doped lithium iron phosphate.
It should be noted that the terms "first," "second," and the like in the description and in the claims of the present application are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the application described herein are, for example, capable of operation in sequences other than those described herein.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The preparation method of the core-shell carbon-coated doped lithium iron phosphate is characterized by comprising the following steps of:
in the presence of a first solvent, chelating an iron source compound, a transition metal compound and tannic acid to obtain a chelate-containing product system, wherein the valence state of transition metal ions in the transition metal compound is more than or equal to 4;
carrying out hydrothermal synthesis reaction on a phosphorus source compound, a lithium source compound and the chelate to obtain a tannic acid coated transition metal ion doped lithium iron phosphate precursor;
sintering the tannic acid coated transition metal ion doped lithium iron phosphate precursor in an inert atmosphere to obtain the core-shell carbon coated doped lithium iron phosphate;
wherein the transition metal ion is selected from Ti 4+ 、W 6+ 、Ta 5+ 、Nb 5+ 、Zr 4+ 、Mo 6+ And V 5+ One or more of the group consisting of chloride, sulfate, nitrate, acetate and organic salt of the transition metal ion;
in the chelation reaction, the ratio of the mole number of the iron ions to the transition metal ions in the tannic acid and the iron source compound is (0.1 to 3): 1: (0.001-0.02);
the molar ratio (1 to 4) of the transition metal ion to the phosphorus source compound in the lithium source compound, the iron source compound, and the transition metal compound: (0.9-1.5): (0.001-0.02): (0.6-1.5);
the temperature of the hydrothermal synthesis reaction is 120-240 ℃, and the sintering temperature of the sintering process is 350-900 ℃.
2. The method for preparing core-shell carbon-coated doped lithium iron phosphate according to claim 1, wherein the transition metal ion is Ti 4+ 。
3. The method for preparing core-shell carbon-coated doped lithium iron phosphate according to claim 1, wherein the hydrothermal synthesis reaction is carried out for 5-48 hours and the pH is 5-8.
4. The method for preparing core-shell carbon-coated doped lithium iron phosphate according to claim 1 or 3, wherein the heat preservation time in the sintering process is 3-12 h;
the temperature rising rate in the sintering process is 2-10 ℃ min -1 The cooling rate after sintering is 2-15 ℃ min -1 。
5. The method for preparing core-shell carbon-coated doped lithium iron phosphate according to claim 4, wherein the temperature rising rate in the sintering process is 5 ℃ min -1 The cooling rate after sintering is 10 ℃ min -1 。
6. The method for preparing core-shell carbon-coated doped lithium iron phosphate according to claim 1, wherein the iron source compound is one or more selected from the group consisting of ferrous chloride, ferrous sulfate, ferrous nitrate, ferric chloride, ferric sulfate, ferric nitrate, ferric phosphate, ferric acetylacetonate, ferric trifluoromethane sulfonate, and ferrocene;
the phosphorus source compound is selected from phosphoric acid and/or monoammonium phosphate; a kind of electronic device with high-pressure air-conditioning system
The lithium source compound is selected from one or more of the group consisting of lithium carbonate, lithium hydroxide, lithium sulfate, lithium acetate, lithium nitrate, lithium trifluoromethane sulfonate, and lithium oxalate.
7. A core-shell carbon-coated doped lithium iron phosphate, characterized in that the core-shell carbon-coated doped lithium iron phosphate is produced by the production method according to any one of claims 1 to 6.
8. The core-shell carbon-coated doped lithium iron phosphate of claim 7, wherein the core-shell carbon-coated doped lithium iron phosphate is LiFe x1- M x PO 4 And @ C, wherein x is 0.001-0.02, and M is a transition metal ion with a valence of 4 or more.
9. A lithium ion battery comprising a positive electrode material, wherein the positive electrode material comprises the core-shell carbon-coated doped lithium iron phosphate of any one of claims 7-8.
10. An electric drive, characterized in that it comprises the lithium ion battery of claim 9.
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| CN116715213A (en) * | 2023-08-10 | 2023-09-08 | 河北顺境环保科技有限公司 | Recycling treatment method of non-injected lithium iron phosphate waste sheet |
| CN117865101A (en) * | 2023-12-11 | 2024-04-12 | 湖北三峡实验室 | Preparation method of low-temperature lithium iron phosphate positive electrode material |
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